如何动态格式化数字以在UITextField条目中包含逗号？

shouldChangeCharactersInRange:您可以使用a NSNumberFormatterDecimalStyle来处理逗号格式,而不是自己插入逗号.即使它被称为"十进制"样式,它也会插入逗号以适当地将数字组合成千位数字.

注意:为了简化问题,我假设您只希望文本字段接受数字条目,我还将添加逻辑以限制用户对数字的输入.

编辑:我已根据OP的请求更新了代码以处理小数.

要NSNumberFormatterDecimalStyle在每个字符条目上使用格式,请尝试将其添加到shouldChangeCharactersInRange:委托方法:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if (([string isEqualToString:@"0"] || [string isEqualToString:@""]) && [textField.text rangeOfString:@"."].location < range.location) {
        return YES;
    }

    // First check whether the replacement string's numeric...
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    bool isNumeric = [string isEqualToString:filtered];

    // Then if the replacement string's numeric, or if it's 
    // a backspace, or if it's a decimal point and the text
    // field doesn't already contain a decimal point,
    // reformat the new complete number using
    // NSNumberFormatterDecimalStyle
    if (isNumeric ||
        [string isEqualToString:@""] ||
        ([string isEqualToString:@"."] &&
         [textField.text rangeOfString:@"."].location == NSNotFound)) {

        // Create the decimal style formatter
        NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
        [formatter setNumberStyle:NSNumberFormatterDecimalStyle];
        [formatter setMaximumFractionDigits:10];

        // Combine the new text with the old; then remove any
        // commas from the textField before formatting
        NSString *combinedText = [textField.text stringByReplacingCharactersInRange:range withString:string];
        NSString *numberWithoutCommas = [combinedText stringByReplacingOccurrencesOfString:@"," withString:@""];
        NSNumber *number = [formatter numberFromString:numberWithoutCommas];

        NSString *formattedString = [formatter stringFromNumber:number];

        // If the last entry was a decimal or a zero after a decimal,
        // re-add it here because the formatter will naturally remove
        // it.
        if ([string isEqualToString:@"."] &&
            range.location == textField.text.length) {
            formattedString = [formattedString stringByAppendingString:@"."];
        }

        textField.text = formattedString;

    }

    // Return no, because either the replacement string is not 
    // valid or it is and the textfield has already been updated
    // accordingly
    return NO;
}

对于Swift 4.0版本的Lyndsey Scott的回答:

   func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if ((string == "0" || string == "") && (textField.text! as NSString).range(of: ".").location < range.location) {
            return true
        }

        // First check whether the replacement string's numeric...
        let cs = NSCharacterSet(charactersIn: "0123456789.").inverted
        let filtered = string.components(separatedBy: cs)
        let component = filtered.joined(separator: "")
        let isNumeric = string == component

        // Then if the replacement string's numeric, or if it's
        // a backspace, or if it's a decimal point and the text
        // field doesn't already contain a decimal point,
        // reformat the new complete number using
        if isNumeric {
            let formatter = NumberFormatter()
            formatter.numberStyle = .decimal
            formatter.maximumFractionDigits = 8
            // Combine the new text with the old; then remove any
            // commas from the textField before formatting
            let newString = (textField.text! as NSString).replacingCharacters(in: range, with: string)
            let numberWithOutCommas = newString.replacingOccurrences(of: ",", with: "")
            let number = formatter.number(from: numberWithOutCommas)
            if number != nil {
                var formattedString = formatter.string(from: number!)
                // If the last entry was a decimal or a zero after a decimal,
                // re-add it here because the formatter will naturally remove
                // it.
                if string == "." && range.location == textField.text?.count {
                    formattedString = formattedString?.appending(".")
                }
                textField.text = formattedString
            } else {
                textField.text = nil
            }
        }
        return false

    }

这是Swift 3中的一个版本.我用它来表示整数,我没有用十进制数来检查.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

     // Uses the number format corresponding to your Locale
     let formatter = NumberFormatter()
     formatter.numberStyle = .decimal
     formatter.locale = Locale.current
     formatter.maximumFractionDigits = 0


    // Uses the grouping separator corresponding to your Locale
    // e.g. "," in the US, a space in France, and so on
    if let groupingSeparator = formatter.groupingSeparator {

        if string == groupingSeparator {
            return true
        }


        if let textWithoutGroupingSeparator = textField.text?.replacingOccurrences(of: groupingSeparator, with: "") {
            var totalTextWithoutGroupingSeparators = textWithoutGroupingSeparator + string
            if string.isEmpty { // pressed Backspace key
                totalTextWithoutGroupingSeparators.removeLast()
            }
            if let numberWithoutGroupingSeparator = formatter.number(from: totalTextWithoutGroupingSeparators),
                let formattedText = formatter.string(from: numberWithoutGroupingSeparator) {

                textField.text = formattedText
                return false
            }
        }
    }
    return true
}

此方法的最大优点是它使用当前语言环境(区域)中定义的分组分隔符,因为并非每个人都使用逗号作为分组分隔符.

使用0,退格键,但是,我再次没有使用小数测试它.如果您使用小数进行处理,则可以自由地增强此代码.

例子:

输入:"2" - >"2"

输入:"3" - >"23"

输入:"6" - >"236"

输入:"7" - >"2,367"

输入:"0"3次 - >"2,367,000"

退格 - >"236,700"

从0起作用:

输入:"0" - >"0"

输入:"2" - >"2"